"Lorem Ipsum" completely confused me the first time I ran into it.
I was trying to make a document for work, using Apple Pages for the first time. Pages had a template that seemed good for the kind of document I had to make so I used that.
The template included "Lorem Ipsum" text. But since I hadn't heard of it before I thought it was some sort of sample document showing how to use the template but in a language I didn't recognize.
I figured that I'd somehow gotten Pages configured to default to a foreign language and spent the next couple of hours trying to figure out how to set it to English. Eventually it occurred to me to search for some of the exact text from the template, hoping to find someone else had already dealt with this problem, and found the Wikipedia article that explained what "Lorem Ipsum" is.
TextEdit's icon used to have a copy of "Here's to the Crazy Ones" letter/poem/whatever. It was barely legible in the days of 256px icons but was extremely legible in the 512px version. I forget when it was first added, IIRC early versions of the icon used Lorem Ipsum text.